Terpenes are organic compounds which may be found in nature or prepared synthetically. Terpenes are derived from isoprene, and may involve cyclic compounds, such as limonene (obtainable from lemon rinds) and valencene (which may be obtained from Valencia oranges), having the structures shown below.
These terpenes have pleasant citrus fragrances; d-limonene is used in cosmetics, food and drug manufacturing, and in environmentally friendly cleaning products.